In the field of drip or trickel irrigation, it is a growing practice to use thin wall irrigation tubes which are essentially flat, when free of pressure and which expand to an essentially cylindrical configuration when pressurized.
When flat, such tubing is easily bitten and punctured at its folded side margins by small rodents. In fact the tube even, when pressurized, may be bitten and punctured as the diameter is often in the range between 5/8 and 3/4 inches (1.5875 cm and 1.905 cm).
Plastic tubing having relatively thick walls have been impregnated with a deterrent chemical which leaches to the surface of the tube and is tasted by the rodent upon initial contact, before biting and penetrating the tube; however, because of the need to deter the rodent on first contact it is necessary to use a chemical which progressively leaches from the tube.
Extrudable plastics have been formulated which contain a deterrent chemical and have been formed into plastic tubes or pipe. A chemical is selected which tends to leach from the outer surface of the pipe to produce a surface having a repellent taste. Such a chemical also leaches into the pipe and thus is effective for only a limited period. Also, the range of chemicals which may be used is limited as it must be compatable with the plastic material, and cannot be toxic.